X-ray imaging apparatus

ABSTRACT

An X-ray imaging apparatus  1  includes an imaging device  31 . Imaging device  31  has a lens  33 , an imaging device  37 , a circuit for driving the imaging device, and a board  53, 57  having a circuit used for processing video signals that are produced from the imaging device. These structural elements of the imaging device  31  are integrally rotatable as one body. Even when an X-ray image intensifier and an X-ray generator are revolved around the object, an output image formed on the output surface can be displayed as an upright image, if required. In addition, only the structural component by which the lens and the board  53  are connected together requires a certain level of precision, so that the cost for preparing the structural components of the apparatus is low as a whole.

TECHNICAL FIELD

The present invention relates to an X-ray imaging apparatusincorporating a camera from which electric image signals are picked up,more specifically to an improvement of a camera section having afunction of rotating an image.

BACKGROUND ART

An X-ray imaging apparatus is useful in examining VISCUS of a human bodyor the interior of an object. X-rays radiated to a human body or anobject are detected as an X-ray transmission concentration distribution,i.e., an X-ray image, and this X-ray image is converted into avisible-light image. The visible-light image is further converted intoelectric image signals, and the X-ray transmission concentrationdistribution or the X-ray image is displayed on a monitor or the like inreal time. Image information is stored in a storage of a computer or thelike, for later use.

An X-ray imaging apparatus is provided with: an X-ray generator forgenerating X-rays; an X-ray image intensifier for intensifying andconverting an X-ray image, i.e., the X-rays which are output from theX-ray generator and have passed through an object, into a visible-lightimage; and a monitor device for displaying an output image which is avisible image obtained by conversion by the X-ray image intensifier. Themonitor device can display the output image in real time, since it usesa camera that images the output image of the X-ray image intensifier andoutputs electric image signals.

X-rays radiated from the X-ray generator pass through an object and areincident on the X-ray image intensifier in the form of an X-ray image.This X-ray image is first intensified by the X-ray image intensifier andis then converted into a visible-light image. This visible-light imageis displayed on the output surface of the X-ray image intensifier as anoutput image.

The output image on the output surface of the X-ray image intensifier isprojected through a lens on the imaging surface of the imaging device ofthe camera. The image projected on the imaging surface of the imagingdevice is converted into electric image signals by the imaging device,and is displayed on the monitor device.

In the X-ray imaging apparatus, the imaging device, including the X-rayimage intensifier and the camera which are arranged to oppose the X-raygenerator, with the object located therebetween, is revolved around theobject in an arbitrary direction and moved to an arbitrary position.

In this type of X-ray imaging apparatus, the camera has to be revolvedaround the object in the opposite direction so that the observer canrotate the image in an arbitrary direction, for the correction of theimage direction.

In the above X-ray imaging apparatus, the camera can be revolved, forexample, in the following method. A board, on which the camera ismounted along with a circuit for driving the camera and a signal circuitfor processing video signals output from the camera, is fixed to adisk-shaped flange. Then, this flange is fixed to a lens support framesecured to the X-ray image intensifier by means of a bearing. In thismanner, the camera is allowed to revolve relative to the X-ray imageintensifier.

However, this method is disadvantageous in that the signal lines andpower supply lines led from the board may be easily twisted when thecamera incorporating the imaging device is revolved. In this case, theangle of revolution of the camera must be restricted so as to preventthe signal lines and power supply lines from being twisted. During theobservation of the object, therefore, the camera may have to be revolvedin the opposite direction so as to move the camera to the intendedrevolving position, which lengthens the time needed for observation.

FIG. 15 is a schematic illustration showing an example of apresently-available X-ray imaging apparatus capable of rotating animage.

As shown in FIG. 15, the X-ray imaging apparatus 101 comprises: an X-rayimage intensifier 111 for intensifying and converting an X-ray image,i.e., X-rays output from the X-ray generator and passing through anobject to be imaged, into a visible-light image; and a camera 121, i.e.,an imaging device, for imaging the output image produced on the outputsurface and converting the output image into image signals, therebyenabling a video image to be displayed on a monitor device (not shown).

A support frame 123 a is secured on the output side of a housing 115 inwhich the X-ray image intensifier 111 is arranged.

The camera 121 is made up of: a lens 123 supported by means of thesupport frame 123 a and spaced from the output image 114 of the X-rayimage intensifier 111 by a predetermined distance; a CCD imaging device127 having a disk shape and positioned at the image focus position on arotatable circuit board 125; a motor 129 for rotating the circuit board125; and a signal transmission mechanism 131 for transmitting outputsignals of the imaging device 127, which are sent thereto from thecircuit board 125, to an external circuit, and for applying drivingpower to the imaging device 127. By the circuit board 125, the imagingdevice 127 is allowed to revolve around the central axis A of avisible-light image transmitted through the lens 123. The circuit board125 is rotatably held by support frame 125 a fixed to the support frame123 a.

The signal transmission mechanism 131 includes: a gear 133 for revolvingthe imaging device 127 and circuit board 125 in such a manner that thecenter of the visible-light image output from the lens 123 coincideswith the axis of revolution; an electrode drum 137 which is coaxial withthe support frame 125 a, is supported by a bearing 135 to be rotatablewith reference to an auxiliary frame 125 b inserted into the supportframe 125 a, and permits the output signal from the imaging device 127to be led to an external circuit; and a plurality of brushes 139 whichare fixed to the auxiliary frame 125 b of the cylindrical support frame125 a and electrically connect ring electrodes 136 of the electrode drum137 to the signal lines and power supply lines. The electrode drum 137is coaxial with the center of rotation on which the circuit board 125and gear 133 are rotated, i.e., with the central axis A of thevisible-light image output from the lens 123.

In the X-ray imaging apparatus 101 shown in FIG. 15, the output signalsof the imaging device 127, which are output by way of the circuit board125, are sent to an external device (not shown) by means of theelectrode drum 137 and brushes 139 of the signal transmission mechanism131.

With this structure, the signal lines and power supply lines attached tothe circuit board 125 do not impose any limit on the angle of revolutionof the imaging device 127.

In the apparatus shown in FIG. 15, however, the electrode drum 137 isused. Due to the use of this drum, the camera 121 is inevitably long inthe direction of the axis around which the camera 121 is revolved.

In addition, the image formed by the camera 121 must be displayed in thecenter of the display screen without reference to the position ofrevolution of the camera 121. Since the center of the image which thelens 123 forms based on the output image 114 of the X-ray imageintensifier 111 must coincide with the center of the imaging surface ofthe imaging device 127, the axis of revolution defined by the revolutionof the imaging device 127 and the center of the imaging surface of theimaging device 127 must coincide with each other. Further, in order toprevent the resolution from becoming low in the peripheral portions ofthe image, the plane in which the lens 123 forms an image by the outputimage 114 must be exactly the same as the imaging surface of the imagingdevice 127. It is therefore required that the central axis of the lens123 and the axis defined by the revolution of the imaging device 127coincide with each other. When the electrode drum 137 is coupled to thebearing 135 and when the bearing 135 is coupled to the auxiliary frame125 b of the support frame 125 a, the tilt angle and the eccentricity ofeach structural member must be within an allowable range. This meansthat the electrode drum 137 and the support frames 125 a and 123 a mustbe fabricated and worked with high precision. This inevitably increasesthe cost required for manufacturing the structural members and the costrequired for assembling them.

Accordingly, an object of the present invention is to provide an X-rayimaging apparatus which enables reduction in both the cost formanufacturing structural members and the cost for assembling them, andwhich includes a camera that is smaller in size and can be revolvedwithout any restriction even when an object is rotated.

The present invention has been made after due consideration of theproblems described above, and is intended to provided an X-ray imagingapparatus comprising: an X-ray image intensifier for converting an X-rayimage into a completely-round output visible-light image; an opticallens assembly for focusing the output visible-light image on apredetermined position; a solid-state imaging device arranged at theposition where the output visible-light image is focused by the opticallens assembly; a signal processing circuit board for driving thesolid-state imaging device and processing output image signals producedtherefrom; a support frame, mechanically fixed to the X-ray imageintensifier, for mechanically supporting the optical lens assembly,solid-state imaging device and signal processing circuit board; and arevolving mechanism for revolving the solid-state imaging devicerelative to the X-ray image intensifier such that an optical center axiscoincides with the center of revolution of the solid-state imagingdevice, the signal processing circuit board being arranged such that theoptical center axis extends therethrough and the solid-state imagingdevice being fixed to the signal processing circuit board, the opticallens assembly being coupled to the signal processing circuit boarddirectly or with another member interposed, such that the optical lensassembly and the signal processing circuit board constitute onemechanical body, a rotating motor being fixed to the support frame androtating the solid-state imaging device, the signal processing circuitboard and the optical lens assembly as one body with reference to thesupport frame, a plurality of slip rings being arranged in theneighborhood of the solid-state imaging device in a concentric mannerand being rotatable together with the solid-state imaging device, andelectric power and output image signals being supplied to thesolid-state imaging device and the signal processing circuit board byway of the slip rings.

In the X-ray imaging apparatus of the present invention, the slip ringsmay be concentrically fixed to the signal processing circuit board or toa flat plate provided independently of the signal processing circuitboard and arranged perpendicular to the optical center axis.

In the X-ray imaging apparatus of the present invention, the opticallens assembly may include an anamorphic lens system incorporating acylindrical lens, and the solid-state imaging device may have arectangular image-receiving surface. In this case, the anamorphic lenssystem forms an elliptical image by enlarging or reducing the outputvisible-light image of the X-ray image intensifier in one direction, andprojects the elliptical image on the rectangular image-receiving surfaceof the solid-state imaging device such that the longer-axis direction ofthe elliptical image and that of the image-receiving surface coincidewith each other.

In the X-ray imaging apparatus of the present invention, the opticallens assembly may be arranged in the space inside the support frame, andthe motor may be arranged in the space surrounding the optical lensassembly.

In the X-ray imaging apparatus of the present invention, the opticallens assembly may include an electrically-driven diaphragm. A signal fordriving this diaphragm is supplied by way of the slip rings.

In the X-ray imaging apparatus of the present invention, a cylindricallens may be used to form an image whose size is reduced in the verticaldirection of the solid-state imaging device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of an X-ray imaging apparatus whichis according to one embodiment of the present invention and whichcaptures an output image formed on the output surface of the X-ray imageintensifier.

FIG. 2 is a schematic illustration showing a direction in which theimaging unit and the X-ray image formation unit-holding device arerevolved in the X-ray imaging apparatus depicted in FIG. 1.

FIG. 3 is a sectional view showing detailed structures of the X-rayimage intensifier and the imaging device employed in the X-ray imagingapparatus depicted in FIG. 1.

FIG. 4 is a partially-enlarged view showing detailed structures of theimaging device, which are fixed to the X-ray image intensifier in themanner shown in FIG. 3.

FIG. 5 is a schematic illustration showing the imaging device and sliprings of the imaging device depicted in FIG. 4.

FIG. 6 is a schematic illustration showing the relationships between theimage-receiving surface of the imaging device shown in FIG. 4 and anoutput image formed on the output surface of the X-ray image intensifierand transmitted through the anamorphic lens.

FIG. 7 is a schematic illustration showing the relationships between theshape of the imaging surface of the imaging device of the imaging deviceand the power of the lens.

FIG. 8 is a schematic illustration showing the relationships between thelight-receiving surface of the imaging device of the imaging deviceshown in FIG. 4 and the aberration of the output image formed on theoutput surface of the X-ray image intensifier and transmitted throughthe anamorphic lens.

FIG. 9 is a schematic illustration showing how the camera and lens ofthe imaging device shown in FIG. 4 are fixed.

FIG. 10 is a partially-enlarged view showing in more detail the mannerin which the camera and lens depicted in FIG. 9 are fixed.

FIG. 11 is a schematic sectional view of an imaging device according toan embodiment different from that shown in FIG. 1.

FIG. 12 is a schematic illustration of an X-ray imaging apparatus whichis according to another embodiment of the present invention and whichcaptures an output image on the output surface of the X-ray imageintensifier.

FIGS. 13A, 13B and 13C are schematic illustrations each showing how thelenses incorporated in the camera of the X-ray imaging apparatus shownin FIG. 12 are adjusted in position.

FIG. 14 shows how the X-ray image intensifier and the camera areassembled.

FIG. 15 is a schematic view showing an example of an imaging device,which is incorporated in a known X-ray imaging apparatus.

BEST MODE OF CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings.

FIG. 1 is a schematic illustration of an X-ray imaging apparatusaccording to one embodiment of the present invention.

As shown in FIG. 1, an X-ray imaging apparatus 1 comprises: an X-raygenerator 11 for generating X-rays; an X-ray image intensifier 13 forintensifying and converting an X-ray image, i.e., X-rays generated bythe X-ray generator 11 and transmitted through an object O, into avisible-light image; a monitor device 21 for enabling an output image ofthe X-ray image intensifier 13, i.e., the visible-light image which theX-ray image intensifier 13 outputs after conversion, to be displayedwith no need to employ a recording medium, such as a film or aphotograph; and a camera 31 for capturing the output image of the X-rayimage intensifier 13 and outputting electric image signals so that themonitor device 21 can display the output image converted from thevisible-light image of the X-ray image intensifier 13.

The output image formed on the output screen 17 a of the X-ray imageintensifier 13 is projected on the rectangular imaging surface of theCCD imaging device 37 of the camera 35 by the anamorphic lens system 33of the camera 31. The visible-light image projected on the imagingsurface of the imaging device 37 is converted into image signals by theimaging device 37. After being subjected to predetermined imageprocessing by an image processing apparatus 39, the image signals aredisplayed on the monitor device 21.

As shown in FIG. 2, the X-ray generator 11, the X-ray image intensifier13 and the camera 31 are revolved with the axis A of revolution as acenter, in such a manner that the X-ray image intensifier 13 and thecamera 31 are opposed to the X-ray generator 11, with the object Olocated between them. By this revolution, the X-ray imaging apparatus 1can observe the object from various directions.

The X-ray generator 11 and the camera 31 are connected together by meansof a C-arm 19 (an arm that is shaped like “C”). With the C-arm rotated,the X-ray generator 11 and the camera 31 image the object O from anarbitrary direction.

In the above X-ray image imaging apparatus wherein the X-ray imageintensifier 11 can be revolved, the C-arm 19, by which the X-ray imageintensifier 13 and the X-ray generator 11 are integrally held, isrotated in direction a so as to observe the object O from variousdirections. In order for the output image of the X-ray image intensifier13 (which image is projected on an imaging device 37 by lens 33) to beoutput on the monitor device 21 with the image of the object O beingdisplayed in the upright state, the imaging device 37 (i.e., the camera31) is rotated in the reverse direction β by an angle corresponding tothe angle for which the X-ray image intensifier 13 is rotated.

FIG. 3 is a sectional view showing how the X-ray image intensifier 13and the camera 31, both employed in the X-ray imaging apparatus shown inFIGS. 1 and 2, are assembled together to constitute an X-ray imagingunit 41.

As shown in FIG. 3, the X-ray image intensifier 13 and the camera 31 ofthe X-ray imaging apparatus 1 shown in FIGS. 1 and 2 are assembled to beintegral with the housing 42 of the X-ray image intensifier 13.

The X-ray image intensifier 13 is defined by a vacuum envelope 14. Atone end of this envelope 14, the X-ray image intensifier 13 has an inputscreen 15 a formed on the inner side of an input window, which is madeof aluminum, for example. At the other end of the envelope 14, i.e., atthe end opposing the input screen 15 a, the X-ray image intensifier 13has an output fluorescent screen 17 a. This screen 17 a is formed on theinner side of an output glass board 17 and outputs a visible-light imagewhich can be captured by the camera 31.

First to third focusing electrodes 18 a-18 c and an anode 19 arearranged between the input screen 15 a and the output screen 17 a.

X-rays generated from the X-ray generator 11 are transmitted through theobject O and are incident on the input screen 15 a of the X-ray imageintensifier 13, thus forming an X-ray image. By the input screen 15 a,the X-ray image is converted into an electronic image. This electronicimage is accelerated and focused by the thirst to third focusingelectrodes 18 a-18 c and the anode 19, and is then converted into avisible-light image by the output screen 17 a.

The X-ray image intensifier 13 is firmly fixed to the housing, forexample at the outer periphery of the input window 15 and the outerperiphery of the output glass 17, by use of insulating members 42 b andsupport poles 42 c.

At the output end of the housing 42, a bottom plate 42 a is arranged.This bottom plate 42 a is mechanically strong, and has an openingcorresponding in position to the output glass 17 and having apredetermined diameter.

The camera 31 is attached to the rear side of the bottom plate 42 a.

A camera flange 43, which is made of a mechanically strong metal disk,is fixed to the rear side of the bottom plate 42 a by means of sixsupport poles 49. A rotatable flange 47, the outer periphery of which ispartly a gear 47 a, is rotatably held by the central portion of thecamera flange by means of a bearing 45. The anamorphic lens 33 issecured on the front side of the rotatable flange 47. A slip ringelectrode board 57 and a circuit board 55 on which the CCD imagingdevice 37 is secured, are integrally fixed to the rear side of therotatable flange 47. These structural components are rotatable endlesslyby a motor 51 fixed to the camera flange 43.

Power and signals are supplied between the circuit board 55 and anexternal device, e.g., a monitor, connected to an external cable 58,through a plurality of slip rings provided on the slip ring electrodeboard 57 and a plurality of brushes 56 kept in contact with the sliprings. The camera 31 is housed in a shield case 35. A high-voltage powersupply cable 42 d extends through the housing 42 and is connected to theX-ray image intensifier.

As described above, the camera 31 includes the lens 33 and the imagingdevice 37 (which is located at the position where the output imagepassing through the lens 33 is focused), and a visible-light imageoutput from the output fluorescent screen 17 a is converted intoelectric signals.

A more detailed description will be given with reference to FIG. 4.

The lens 33 is held by the rotatable flange 47 in such a manner as to berotatable around the central axis A passing through the output screen 17a of the X-ray image intensifier 13. The rotatable flange 47 isrotatably held at the substantial center of the camera flange 43 bymeans of the bearing 45, and the rotatable flange 47 is spaced from theoutput screen 17 a of the X-ray image intensifier 13 by a predetermineddistance by means of the bottom plate 42 a.

The lens 33 is an electrically-driven zoom lens and includes: anelectrically-driven diaphragm 33 a whose aperture can be adjusted by anaperture stop motor (not shown) in response to an external controlsignal; a number of lenses for changing a magnifying power by changingthe distance by an electrically-driven zoom mechanism 33 b of a zoommotor for varying the magnifying power (not shown) in response to anexternal control signal.

A plurality of contact brushes 56 are provided for the camera flange 43.These brushes 56 are in contact with the slip rings, which will bedetailed later with reference to FIG. 5. The brushes 56 maintainelectric connection to the slip rings irrespective of the rotation ofthe rotatable flange 47, and do not impose any restrictions on therotation of the rotatable flange 47. The brushes 56 are arranged on therespective concentric circles, which are defined with the axis A ofrotation as a center.

The camera flange 43 is supported by the six support poles 49 such thatthe imaging device 37 fixed to the circuit board 55 is located in thecenter of the camera flange 43. The central axis of the imaging device37 is made to coincide with the axis of the lens 33, i.e., the axis A ofrotation.

A gear 53 is arranged radially inward of the circle that passes throughthe positions where the support poles 49 are provided. The gear 53engages with the gear 47 a of the rotatable flange 47 and serves totransmit the torque of the motor 51 to both the rotatable flange 47 andthe lens 33 connected thereto.

The imaging device 37, a driving circuit (not shown) for driving theimaging device 37, and a circuit board 55 has a circuit section 39including an image processing circuit for processing video signalsproduced by the photoelectric conversion by the imaging device 37, arefixed to the rotatable flange 47.

The board 57 having a number of slip rings 57 a is located between thegear 47 a and the circuit board 55 mounted with the cylindrical endportion of the rotatable flange 47. The circuit board 55 and the board57 are firmly fixed to the rotatable flange 47 by means of fourinsulating spacers 58 a and four screws 586. The spacers 58 a areinterposed between the board 57 and the circuit board 55, so that theseboards are spaced from each other by a predetermined distance.

As shown in FIG. 5, the board 57 has a number of concentric electrodes,i.e., slip rings 57 a, which are formed with the axis A of rotation as acenter. The signal lines and power supply lines led from the circuitboard 55, and the drive signal lines led from the electrically-drivendiaphragm 33 a of the lens 33 and the electrically-driven zoom mechanism33 b are connected to the slip rings 57 a.

The circuit board 55 holding the imaging device 37 in the center of itand the board 57 are integrally formed as one body, with the rotatableflange 47 being used as a support member.

With this structure, the torque of the motor 51 fixed to the cameraflange 43 is transmitted to the gears 53 and 47 a which are inengagement with each other, and the circuit board 55 and the board 57are rotated by an arbitrary angle in an arbitrary direction in anendless manner. By means of the slip rings 57 a of the board 57 and thebrushes 56, power can be reliably supplied to the circuit board 55 andthe lens 33, and the video signals output from the imaging device 37 canbe reliably sent, without being restricted by the rotating angle of therotatable flange 47.

The lens 33 and the imaging device 37 are integrally rotated by thecylindrical section of the rotatable flange 47, and a substantiallycircular output image output from the substantially circular outputfluorescent screen 17 a of the X-ray image intensifier 13 is incident onthe imaging surface of the imaging device 37. In this case, the axis ofthe lens 33, i.e., the axis A of rotation, and the center point of theimaging surface of the imaging device 37 are not shifted from eachother.

The circuit board 55 and the board 57 are made of comparatively thindisks arranged in planes perpendicular to the central axis A, and arelocated close to each other. In addition, the lens 33 is fixed to thefront portion of the rotatable flange 47. Accordingly, the size of theX-ray imaging apparatus, i.e., the length measured in the axialdirection, is less than the corresponding length of the conventionalapparatus shown in FIG. 15.

Although the high working precision is required in order to permit theaxis A of rotation to coincide with the central axis of the lens 33during the rotation of the camera 31, the structural componentsrequiring such high working precision are limited to the rotatableflange 47 in the case of the present invention. In other words, sinceonly the rotatable flange 47 has to be worked with high precision, themanufacturing cost can be reduced, accordingly.

Let us assume that the output screen 17 a of the X-ray imagingintensifier 13 has a diameter of 30 mm, and that the aspect ratio of thelight-receiving surface of the CCD imaging device 37 is 4:3 and at alength of one side is 17 mm, for example. In this case, the distance Ebetween the output screen 17 a and the front end of the lens 33 and thedistance F between the rear end of the lens 33 and the imaging surface37 a of the CCD imaging device 37 satisfy the relationship F=E/2.Although the depth of focus of the lens of the imaging device is of asmall value, the lens 33 and the imaging device 37, both fixed to therotatable flange 47, are rotated as one body. Hence, the optical axisdoes not move and the out-of-focus state hardly occurs.

A detailed description will be given of the relationships between theanamorphic lens 33 and the imaging device 37 of the camera 31.

Referring to FIG. 6, an optical image P output from the output screen 17a of the X-ray image intensifier 13 is condensed in the verticaldirection by the cylindrical lens 33 c of the anamorphic lens 33, and isprojected on the horizontally-elongated rectangular surface 37 a of thesolid-state imaging device 37 as an elliptical optical image C.

The anamorphic lens 33 shown in FIG. 1 is made up of a cylindrical lenssystems 33 c including one or more lenses, and a single-focus lenssystem 33 d. As shown in FIG. 7, the substantially circular output imageP of the X-ray image intensifier 13 is condensed in the direction Qcorresponding to the shorter sides of the imaging surface of the imagingdevice 37 so that the substantially circular output image P can beinscribed in the outer periphery of the rectangular imaging surface 37 aof the imaging device 37.

A description will now be given with reference to FIG. 8 as to how theadverse effects of the aberration of the cylindrical lens system can besuppressed by condensing a circular image in the vertical direction andprojecting it on the rectangular imaging surface of the CCD element.

The aberration of the cylindrical lens system is marked in the directionin which the magnification of an image is varied, and is not so in itsperpendicular direction. As shown in FIG. 8, there are two methods inwhich a circular image is converted into an elliptical image by theanamorphic lens incorporating a cylindrical lens system, and in whichthe resultant image is formed on the imaging surface of the solid-stateimaging device.

One of the two methods is to first form a circular image B on theimaging surface 37 a without using the cylindrical lens system in such amanner that the circular image is in contact with the upper and lowersides of the imaging surface 37 a. Then, this circular image B iselongated in the horizontal direction by using the cylindrical lenssystem, thereby forming an elliptical image A. The other method is tocondense a circular image P in the vertical direction by using thecylindrical lens system in such a manner that the condensed image is incontact with the right and left sides of the imaging surface 37 a. Thelatter method is used in the embodiment of the present invention.

With the anamorphic lens incorporating a cylindrical lens system, it ispossible to perform either of these methods. The former method isdisadvantageous in that aberration is caused in the horizontal directionin which an image is elongated, resulting in a degradation of thehorizontal resolution. On the other hand, the latter method isdisadvantageous in that aberration is caused in the vertical direction.

In general, the television system of an X-ray imaging apparatus is anNTSC system, and the number of scanning lines is 525 according to thespecifications.

Of these 525 lines, the number of scanning lines that appear on theeffective area of the screen is 485 or so. In the effective imaging areaof the solid-state imaging device, therefore, 485 pixels are arranged ina vertical direction. In the case of a 400,000-pixel CCD solid-stateimaging device, the use of which is very common in an X-ray imagingapparatus, the number of pixels arranged in the horizontal direction ofthe effective imaging area of the imaging device is 768, and all thesepixels in the horizontal direction are used in the center of theeffective imaging area. Since the resolution of the solid-state imagingdevice camera is determined by this number of pixels, the verticalresolution is inferior to the horizontal resolution. This holds true ofthe PAL television system and the SECAM television system as well. Theresolutions of the solid-state imaging device camera of the NTSC systemwill be considered by way of example. In the case where an output imageof the X-ray image intensifier is 15 mm, the horizontal resolution ofthe output screen is 51.2 lines/mm (768 lines÷15 mm), while the verticalresolution of the output screen is 32.3 lines/mm (485 lines÷15 mm). Thatis, the vertical resolution is lower than the horizontal resolution in40%. This means that even if the vertical resolution of an imageprojected on the imaging surface of the CCD solid-state imaging deviceis lower than the horizontal resolution of the same image in 40% or so,such a resolution inferiority is considered allowable in practice.

As described above, the direction in which the resolution is lowered asa result of the aberration should be controlled to be the verticaldirection of the solid-state imaging device. By this control, thedegradation of the vertical-direction resolution arising from thevertical-direction aberration of the cylindrical lens becomes allowable,as long as that degradation is less than 40% of the degradation of thehorizontal-direction resolution. This means that the aberration of thecylindrical lens system of the present invention is negligible inpractice. Since a number of lenses need not be added for the correctionof the adverse effects of the aberration, the anamorphic lens system canbe made of a single cylindrical lens.

The aberration the anamorphic lens has on a projected image isattributed to the single-focus lens system as well, and the aberrationof the single-focus lens occurs equally in all directions. Although theaberration of the single-focus lens system should be small, asingle-focus lens system having a small aberration can be easilydesigned by employing a number of spherical lenses. It should be notedthat a single-focus lens system made up of spherical lenses iscomparatively low in price.

In order to permit the circular output image P of the X-ray imageintensifier 13 to be focused on the rectangular imaging surface of theCCD imaging device as an elliptical image C, the elliptical image C hasto be controlled in such a manner that the longer-axis direction thereofcoincides accurately with the horizontal direction of the imagingsurface 37 a, i.e., the direction of the longer sides thereof.

FIGS. 9 and 10 show a structure for making fine adjustment of the shapeof the elliptical image C. Referring to the Figures, a lens assembly 61incorporating an anamorphic lens 33 is fixed to the camera 31 by meansof a fixing member 62. The lens assembly 61 can be tilted at anarbitrary angle with reference to the fixing member 62, and can be madeimmovable by means of a fixing screw 63. The fixing member 62 is coupledto the rotatable flange 47 by threadably inserting its screw portion 62which is a standardized screw called a “C-mount” into the correspondingfemale screw portion.

To set the lens assembly 61 in the camera 32, the fixing member 62 isattached to the lens assembly 61 beforehand, and the fixing member 62 isthreadably inserted into the corresponding female screw portion of therotatable flange 47. At the time, the angle of the anamorphic lens 33 isindefinite with reference to the solid-state imaging device 37. Then,the entire X-ray imaging apparatus 1 is operated, and the lens assembly61 is rotated while simultaneously looking at the image on thetelevision monitor, until the image on the television monitor becomescircular. After making fine adjustment, the lens assembly 63 is fixed atthe position that enables a completely circular image to be accuratelydisplayed, by fastening the fixing screw 63.

Let us assume that the aspect ratio of the imaging surface 37 a is 3:4.In this case, the longer axis (horizontal axis) of an elliptical opticalimage is {fraction (4/3+L )} times longer than the shorter axis(vertical axis) of the elliptical optical image, and this image isprojected in such a manner as to be in contact with the upper, lower,right and left sides of the imaging surface 37 a. The video signalscorresponding to the elliptically distorted image produced by the camerais condensed only in the horizontal direction by the image processingapparatus 39, and is displayed on the CRT television monitor as acircular image similar to the output optical image of the X-ray imageintensifier.

A CRT television monitor 21 having a deflection size of 1:1 may beemployed. In this case, video signals are supplied thereto withoutpassing through the image processing apparatus 39, so as to form acircular image on the monitor 21. The circular image is formed merely byreducing the amplitude of the horizontal deflection of the CRTtelevision monitor.

In the foregoing embodiment, the entire anamorphic lens assembly isrotatable with reference to the fixing member with which to fix the lensassembly to the camera. This, however, in no way restricts the presentinvention. For example, one or some lenses having an optical poweracting in the same direction may be selected from the anamorphic lenssystem and designed to be rotatable.

Needless to say, the connection between the lens assembly and the camerais not limited to the threadable insertion. As described above, thewhole of the lens assembly or part of the lens system can be rotated inan arbitrary direction, with the anamorphic lens system fixed to thecamera. With this structure, the two perpendicular directions betweenwhich the power of a lens differs can be made to correspond accuratelyto the horizontal and vertical directions of the solid-state imagingdevice, respectively. Therefore, when the solid-state imaging devicecamera and the lens are assembled in the apparatus, it is not necessaryto employ a specially-designed fitting mechanism. Where the fittingmechanism is, for example, a threadable insertion type, themanufacturing cost is low. When the camera of the solid-state imagingdevice is assembled, the lens fitting mechanism need not be worked withparticularly high precision, and the camera can be easily manufactured,accordingly. In addition, the anamorphic lens system and the solid-stateimaging device camera can be assembled by utilization of a C-mount,which is a standardized screw system widely employed in an ordinary lensor camera. Since the C-mount can be used incorporated in an inexpensivegeneral-purpose solid-state imaging device camera, an X-ray imagingapparatus obtained thereby is comparatively low in price.

In the embodiment described above, the cylindrical lens 33 of theanamorphic lens 33 is made of a single cylindrical lens, but may be madeof a number of cylindrical lenses. In addition, the cylindrical lens 33c and the single-focus lens system 33 d may be housed in differentcasings though they may be arranged in the same housing in the aboveembodiment. The use of the cylindrical lens in the anamorphic lens 33 isadvantageous in that the resultant anamorphic optical system is smallerin size and lower in price than an anamorphic lens system employing anexpensive prism lens.

FIG. 11 is a schematic illustration showing another embodiment of thecamera depicted in FIG. 4. In FIG. 11, the same reference numerals orsymbols as in FIG. 4 are used to denote the corresponding or similarstructural elements, and a detailed description of them will be omittedherein. In the camera 31 shown in FIG. 11, a CCD imaging device 37, acircuit section 39 and slip rings 57 a are provided on the same board55.

This structure permits the camera to be short in the axial direction, sothat an X-ray imaging apparatus provided can be made compact in size.

The embodiment shown in FIGS. 12-14 is directed to an X-ray imagingapparatus wherein a single camera 31 can be combined with a number oftypes of X-ray image intensifiers having output fluorescent screens ofdifferent diameters, and wherein a similar or substantially similarimage can be projected on the CCD imaging device.

There are a variety of types of X-ray image intensifiers used ingeneral, and the circular output optical images produced by them havediameters of 15 mm, 20 mm, 25 mm, 30 mm, etc. In addition, thesolid-state imaging devices (e.g., CCD imaging devices) have imagingsurfaces of many different sizes, such as {fraction (2/3+L )}-inch,{fraction (1/2+L )}-inch, {fraction (1/3+L )}-inch format sizes.

Therefore, a large number of anamorphic optical system apparatuses haveto be prepared, depending upon combinations between X-ray imageintensifiers and solid-state imaging devices. In order to vary thereduction rate of the anamorphic optical system of the foregoingembodiment, one of the three lens systems has to be replaced withanother. Since recently-provided systems are designed to be compact insize and free of maintenance by integrally incorporating an opticaldevice, a solid-state imaging device and related signal processingcircuit elements in the same housing as the X-ray image intensifier, itis not desirable to prepare a large number of devices and use them incombination.

This embodiment is intended to solve this problem and the object thereofis to provide an X-ray imaging apparatus capable of changing the imagemagnification by use of an anamorphic optical system of a specific lensstructure. To achieve this object, the anamorphic optical system of theX-ray imaging apparatus is made up of a single-focus lens system havinga number of lenses, and a cylindrical lens system having two or morelenses. One or more of the lenses of the cylindrical lens system aremoved in the optical axis direction to an arbitrary or predeterminedposition with reference to the other lenses.

In the embodiment, the anamorphic lens 33 includes a cylindrical lenssystem 32 made up of two cylindrical lenses 32 a and 32 b that arearranged on the side of the X-ray image intensifier. The anamorphic lens33 also comprises a single-focus lens system 33 d made up of a number ofspherical lenses that are arranged on the side of the solid-stateimaging device. Of the two cylindrical lenses, that cylindrical lens 32a which is located closer to the X-ray image intensifier is movable inthe optical axis direction with reference to the other.

In the anamorphic lens 33, the lens activity of the cylindrical lenssystem 32 can be controlled independently of that of the single-focuslens system 33 d by moving one of the lenses of the cylindrical lenssystem 32 independently of the other. Therefore, the lens activityacting only in the direction in which the cylindrical lens system andthe single-focus lens system have a lens activity can be changed, andthe focusing position can be controlled to coincide with the positionwhere an image is focused only by the lens activity of the single-focuslens system.

FIGS. 13 show how the lenses, output images Pa, Pb and Pc of the X-rayimage intensifier 13, the position of the imaging surface 37 a of thesolid-state imaging device 37, and the diameters of images are relatedto one another when the anamorphic lens 33 mentioned above is employed.FIG. 13A shows the case where the output optical image Pa of the X-rayimage intensifier 13 is 25 mm in diameter, FIG. 13B shows the case wherethe output optical image Pb is 20 mm in diameter, and FIG. 13C shows thecase where the output optical image Pc is 15 mm. The imaging surfaces 37a of the solid-state imaging devices of these cases have the same size.

In the above cases, the distances between the output optical image ofthe X-ray image intensifier and the imaging surface of the solid-stateimaging device are denoted by D1 a, D1 b and D1 c, the distances betweenthe imaging surface of the solid-state imaging device and the lens 33are denoted by D2 a, D2 b and D2 c, the distances between the twocylindrical lenses 32 a and 32 b are denoted by D3 a, D3 b and D3 c, andthe distances between the X-ray image intensifier and the cylindricallens 32 a arranged close thereto are denoted by D4 a, D4 b and D4 c. Thedistances are variable. It should be noted, however, that the positionalrelationships and distances between the cylindrical lens 32 b arrangedcloser to the solid-state imaging device and the single-focus lenssystem 33 are fixed.

An elliptical image C having the same size as the imaging surface 37 aof the solid-state imaging device can be formed by varying thedistances.

In other words, even in the cases where the output optical images P ofthe X-ray image intensifiers are 25 mm, 20 mm and 15 mm in diameter, anelliptical image C of the same size is formed on the imaging surface 18a of the solid-state imaging device.

In these cases, the distances indicated in FIGS. 13 are as follows:

D1 a>D1 b>D1 c,

D2 a<D2 b<D2 c,

D3 a>D3 b>D3 c, and

D4 a>D4 b>D4 c.

FIG. 14 shows how the X-ray image intensifier, the anamorphic lens andthe solid-state imaging device are combined together, and illustrates aspecific mechanism that employs these structural elements to change thedistances. Referring to this Figure, the cylindrical lens 32 a locatedcloser to the X-ray image intensifier is supported by a support member71, in such a manner as to be movable along a casing 72 in the opticalaxis direction. By this movement, the distance D3 between thecylindrical lenses 32 a and 32 b can be adjusted. In the Figure,illustration of a structure for enabling the movement is omitted.

The cylindrical lens 32 b located closer to the solid-state imagingdevice and the lenses of the single-focus lens system 33 d are supportedby another support member 73, and these lenses are movable as one bodyalong the casing 72 in the optical axis direction.

The casing 72 of the anamorphic lens 33 is provided with a male screw ata position where it is connected to the rotatable flange. The rotatableflange 47 is provided with a female screw at the corresponding position.The casing 72 and the rotatable flange 47 are connected together by thescrews.

The distance D2 between the imaging surface of the solid-state imagingdevice and the anamorphic lens 33 is coarsely determined by interposinga ring-like spacer 74 between the casing 72 and the rotatable flange 47.A fine adjustment of the distance D2 can be made by moving the supportmember 73 inside the casing. The distance between the output fluorescentscreen 17 a of the X-ray image intensifier and the imaging surface 37 aof the solid-state imaging device 37 can be adjusted by properlydetermining the length of the support poles 49, which are providedbetween the bottom plate 42 a and the camera flange 43 to connect themto each other.

If the diameters of the output images of the X-ray image intensifier ofthe X-ray imaging apparatus are several in number, or if the sizes ofthe imaging surfaces of the solid-state imaging devices are several innumber, then the positions to which the cylindrical lens is moved andfixed can be limited to be several in number. This simplifies theadjustment required.

As described above, in the anamorphic lens 33, one of the lenses of thecylindrical lens system is movable with reference to the other in theoptical axis direction. Since different magnifications are attained bythat movement, elliptical images of the same size can be formed on theimaging surface of the slid-state imaging device. In this manner, astructure made up of a single optical lens and an imaging device can beused to cope with output images of various diameters formed by the X-rayimage amplifying tube.

The above description was given referring to the case where the imagingsurfaces of the solid-state imaging devices had the same size. Even thecase where the imaging surfaces of the solid-state imaging surfaces havedifferent sizes can be coped with by changing the distance between thelens system and the position of an image in the manner described above.

As described above, this embodiment is applicable to an X-ray imageintensifier that employs a single optical system and outputs images ofdifferent diameters, or to solid-state imaging devices having imagingsurfaces of different sizes. Since, therefore, a large number ofanamorphic optical systems having different powers are not needed, it ispossible to realize an X-ray imaging apparatus that is low in price as awhole.

In recent years, a CCD sensor having a substantially square imagingsurface is developed. In the case of this type of CCD sensor, it is notnecessary to employ an anamorphic lens.

As described above, an X-ray imaging apparatus comprises a camerawherein a lens, an imaging device, a circuit for driving the imagingdevice, and a board having a circuit used for processing video signalsthat are produced from the imaging device are integrally rotatable asone body. Even when an X-ray image intensifier and an X-ray generatorare revolved around an object, an output image formed on the outputsurface can be displayed as an upright image, if required. In addition,with the structure described above, it is possible to provide an X-rayimaging apparatus which enables the X-ray image intensifier, the lensand the imaging device to align with one another, with no significanterror, which prevents a defocused state, and which can be manufacturedat low cost.

What is claimed is:
 1. An X-ray imaging apparatus comprising: an X-rayimage intensifier for converting an X-ray image into a completely-roundoutput visible-light image; an optical lens assembly for focusing theoutput visible-light image on a predetermined position; a solid-stateimaging device arranged at the predetermined position where the outputvisible-light image is focused by the optical lens assembly; a signalprocessing circuit board for driving the solid-state imaging device andprocessing output image signals produced therefrom; a support frame,mechanically fixed to the X-ray image intensifier, for mechanicallysupporting the optical lens assembly, the solid-state imaging device andthe signal processing device circuit board; and a revolving means forrevolving the solid-state imaging device relative to the X-ray imageintensifier such that an optical center axis coincides with a center ofrevolution of the solid-state imaging device, said signal processingcircuit board being arranged such that the optical center axis extendstherethrough, and said solid-state imaging device being fixed to thesignal processing circuit board and having a rectangular image-receivingsurface, said optical lens assembly being mounted on the signalprocessing circuit board, such that the optical lens assembly and thesignal processing circuit board constitute one mechanical body, saidoptical lens assembly being provided in one of a state wherein saidoptical lens assembly is directly mounted on the signal processingcircuit board and a state wherein another member is interposed betweensaid optical lens assembly and the signal processing circuit board, saidsupport frame holding a rotating motor fixed thereto, and said motorrotating the solid-state imaging device, the signal processing circuitboard and the optical lens assembly as one body with relative to thesupport frame, a plurality of slip rings being arranged close to thesolid-state imaging device in a concentric manner and being rotatabletogether with the solid-state imaging device, and electric power andoutput image signals being supplied to the solid-state imaging deviceand the signal processing circuit board by way of the slip rings.
 2. TheX-ray apparatus according to claim 1, wherein said slip rings areconcentrically fixed to one of the signal processing circuit board and aflat plate provided independently of the signal processing circuit boardand arranged perpendicular to the optical center axis.
 3. The X-rayimaging apparatus according to claim 1, wherein said optical lensassembly includes an anamorphic lens system incorporating a cylindricallens, said anamorphic lens system forming an elliptical image byenlarging or reducing the output visible-light image of the X-ray imageintensifier in one direction, and projects the elliptical image on therectangular image-receiving surface of the solid-state imaging devicesuch that longer-axis directions of the elliptical image and theimage-receiving surface coincide with each other.
 4. The X-ray imagingapparatus according to claim 3, wherein said optical lens assemblyincludes a fine adjustment mechanism for making fine adjustment of anangular position to which the solid-state imaging device is revolvedaround the optical center axis and for positioning the solid-stateimaging device at the angular position.
 5. The X-ray imaging apparatusaccording to claim 1, wherein said optical lens assembly is arranged ina space inside the support frame, and said motor is arranged in a spacesurrounding the optical lens assembly.
 6. The X-ray imaging apparatusaccording to claim 1, wherein said optical lens assembly includes anelectrically-driven diaphragm, said diaphragm being driven by a drivingsignal supplied by way of the slip rings.
 7. The X-ray imaging apparatusaccording to claim 3, wherein said optical lens assembly includes asingle-focus lens system made up of a plurality of lenses, and acylindrical lens system made up of two or more lenses, at least one ofthe lenses of the cylindrical lens system being movable in anoptical-axis direction to an arbitrary or predetermined position withreference to other lenses.
 8. The X-ray imaging apparatus according toany one of claims 3, 4 and 7, wherein said cylindrical lens form animage whose size is reduced in a vertical direction of the solid-stateimaging device.